A review of equine sepsis

Retrospective cohort study on diseases and risk factors associated with death in hospitalized neonatal foals

BACKGROUND

The care of sick neonatal foals is labor-intensive and costly. Prediction of risk of death upon admission is often difficult but might support decision-making.

OBJECTIVES

To determine diseases and risk factors associated with death in neonatal hospitalized foals.

ANIMALS

Two hundred twenty-two hospitalized foals, ≤7 days old.

METHODS

Retrospective cohort study. Clinical and laboratory variables were evaluated for their association with death by means of Cox survival analysis and by classification and regression tree (CART) analysis.

RESULTS

Most prevalent diseases were sepsis (43.9%), enteritis (14.0%), and omphalitis (9.0%). Case fatality rate was 33.3%. Neonatal sepsis significantly increased the risk of death (hazard ratio [HR] = 1.9; 95% confidence interval [CI] = 1.2-3.0; P = .009). Multivariable Cox regression in foals ≤7 days old revealed comatose mental state (HR = 2.9; 95% CI = 1.1-8.1; P = .04), L-lactatemia (≥373.8 mg/L [4.2 mmol/L]; HR = 4.4; 95% CI = 1.7-11.7; P = .003) and increased serum amyloid A (SAA; ≥2054 μg/mL; HR = 3.9; 95% CI = 1.2-12.7; P = .02) as risk factors for death, with a sensitivity and specificity of 7.5% and 95.7%, respectively. The CART analysis highlighted L-lactatemia, comatose mental state, and hypercapnia as risk factors for death, with a sensitivity of 38.1% and specificity of 86.1% after validation.

CONCLUSIONS AND CLINICAL IMPORTANCE

In this study sample, sepsis was associated with the highest risk of death. Identified risk factors such as SAA, L-lactate, and comatose mental state might guide veterinarians and owners in better decision-making for economic or welfare reasons. Frequently measured laboratory variables, such as blood glucose concentration and Immunoglobulin G, were not sensitive and specific enough to provide reliable decision support for survival estimation.

A Comparative Review of Cytokines and Cytokine Targeting in Sepsis: From Humans to Horses

With the emergence of COVID-19, there is an increased focus in human literature on cytokine production, the implications of cytokine overproduction, and the development of novel cytokine-targeting therapies for use during sepsis. In addition to viral infections such as COVID-19, bacterial infections resulting in exposure to endotoxins and exotoxins in humans can also lead to sepsis, resulting in organ failure and death. Like humans, horses are exquisitely sensitive to endotoxin and are among the veterinary species that develop clinical sepsis similar to humans. These similarities suggest that horses may serve as a naturally occurring model of human sepsis. Indeed, evidence shows that both species experience cytokine dysregulation, severe neutropenia, the formation of neutrophil extracellular traps, and decreased perfusion parameters during sepsis. Sepsis treatments that target cytokines in both species include hemoperfusion therapy, steroids, antioxidants, and immunomodulation therapy. This review will present the shared cytokine physiology across humans and horses as well as historical and updated perspectives on cytokine-targeting therapy. Finally, this review will discuss the potential benefits of increased knowledge of equine cytokine mechanisms and their potential positive impact on human medicine.

Pleural Empyema in Six Horses: A Retrospective Case Series

The clinical findings of pleural empyema in six horses were retrospectively studied using epidemiological, clinical pathology, microbiological, ultrasound, and post-mortem data. The clinical findings included tachycardia (n = 3/6), tachypnea (n = 6/6), cyanotic mucosa (n = 2/6), hyperthermia (n = 4/6), inspiratory or mixed dyspnea (n = 6/6), presence of fluid and/or pleural rubbing (n = 2/6) and coarse crackling on auscultation (n = 4/6). Horses demonstrated leukocytosis (16.22 × 103/µL) with neutrophilia (12.32 × 103/µL) and hyperfibrinogenemia (633.33 mg/dL) and an increase in urea (69.80 mg/kg) and globulins (5.22 g/dL). The pleural fluid exhibited exudate (n = 5/6). The pathogens isolated from transtracheal wash (TTW) and/or pleural effusion included Aspergillus fumigatus, Enterobacter cloacae, alpha and beta hemolytic Streptococcus, Pseudomonas aeruginosa, Salmonella sp., Streptococcus equi subsp. zooepidemicus, and beta hemolytic Staphylococcus. The in vitro tests of microbial sensitivity of the isolates revealed that ceftiofur (5/6) and penicillin (3/6) were the most effective drugs. The fatality rate was 83% (5/6). The main post-mortem finding was the presence of fibrin in the pleural cavity with adhesion between the parietal and visceral pleura. These results show that pleural empyema is a complex disease pathophysiology that is refractory to conventional treatment.

Equine Placentitis in Mares Induces the Secretion of Pro-Inflammatory Cytokine eIL-1β and the Active Extracellular Matrix Metalloproteinase (MMP)-9

Equine placentitis is characterized by infection and inflammation of the placenta. Different biomarkers associated with this inflammatory response have been evaluated in experimentally induced equine placentitis, but not in pregnant mares with spontaneous placentitis. The aim of the current study was to determine the concentration of eIL-1β and the activity of proMMP-2 and proMMP-9 in the serum of healthy mares and mares with placentitis on days 240 and 320 of gestation to explore whether these biomarkers are associated with equine maternal placentitis and/or with the birth of an infected or inviable foals. Serum samples were collected from sixteen pregnant English Thoroughbred mares, retrospectively classified as follows: (1) healthy mares with full-term gestation; and (2) mares with ultrasonographic signs of placentitis. The health of each foal was examined at birth, and it was decided to classify the cases into four groups: (1) healthy mares delivering a healthy foals (HM-HF, n = 6); (2) mares with USP delivering a healthy foal (USP-HF, n = 3); (3) mares with USP delivering a live septic foal (USP-LSeF, n = 4); and (4) mares with USP delivering a dead foal (USP-DF, n = 3). eIL-1β was quantified by ELISA, and proMMP-2 and proMMP-9 activity by gelatin zymography electrophoresis. In healthy mares, the serum concentrations of eIL-1β underwent a significant 16.5-fold increase from day 240 to day 320 of gestation. Although similar results were found in the mares with ultrasonographic signs of placentitis that delivered a healthy foal, those delivering a live septic or nonviable foal exhibited much higher concentrations of eIL-1β. proMMP-2 and proMMP-9 activity was not associated with maternal placentitis, foal infection, or death. Hence, the presence of placentitis severe enough to affect the health of the foal can be confirmed or discarded by determining the eIL-1β concentration in mares that have shown ultrasonographic signs of placentitis.

Red blood cell distribution width to platelet ratio in neonatal foals with sepsis

BACKGROUND

Rapid and accurate markers to aid diagnosis of sepsis are needed in neonatal foals. The CBC variable red blood cell distribution width (RDW) to platelet ratio (RPR) is associated with inflammatory response and linked to poor outcomes of sepsis in human patients.

HYPOTHESIS

Explore the correlation of RPR with sepsis in neonatal foals and evaluate RPR predictive and prognostic value.

ANIMALS

Three hundred seventeen hospitalized neonatal foals ≤7 days of age that had a CBC and physical exam performed at admission between 2012 and 2021.

METHODS

Retrospective case-control study. Clinical records were used to calculate sepsis scores and define groups. Red blood cell distribution width to platelet ratio was calculated and compared between groups (septic vs nonseptic) based on Kruskal-Wallis and Wilcoxon signed-rank tests. A multivariate logistic regression model to predict sepsis was created. The cutoff for RPR was obtained based on the maximal Youden Index. The Kaplan-Meier method and the log-rank test were used to estimate survival curves and compare survival rates based on RPR.

RESULTS

Red blood cell distribution width to platelet ratio was significantly higher in septic foals (Median = 0.099, confidence interval [CI] [0.093; 0.108]) than in sick nonseptic (0.085, CI [0.083; 0.089]) and healthy foals (0.081, CI [0.077; 0.086]; P < .0001). Red blood cell distribution width to platelet ratio was able to predict sepsis with high accuracy (AUC = 82.1%). The optimal RPR cutoff for sepsis was 0.09.

CONCLUSIONS AND CLINICAL IMPORTANCE

Red blood cell distribution width to platelet ratio calculation is practical, inexpensive, and based on CBC-derived data. Calculation of RPR along with CBC can aid in the diagnosis of sepsis and estimation of outcome.

Use of Milk Thistle in Farm and Companion Animals: A Review

Milk thistle, Silybum marianum, is a medicinal plant grown for its bioactive compounds with well-documented antioxidant and hepatoprotective properties. Milk thistle has a well-established pharmacological reputation for treatments of human liver disease, but it is also used in animals. This review summarizes the experimental evidence of milk thistle's effects on animals when administered as silymarin extract (feed additive) or a feed ingredient, if administered as seed or expeller/cake with the seed residue still containing the bioactive components. The use as a feed additive or feed ingredient is motivated by the complexity of silymarin registration as a veterinary drug. In farm animals, the drug improves the animals' performance and product quality and oxidative stability, supports liver function during the productive life-cycle, improves gut-health and morphology, and can reduce intestinal pathogens. In dogs and cats, the treatment is focused on acute and chronic liver diseases including the detoxification processes and support of drug treatments including chemotherapy. In equine athletes, milk seed cake showed positive effects and a faster return of cortisol to the resting values before exercise occurred. In aquaculture, it confirms its usefulness in supporting animal health and performance. In certain studies it is not clear what has been administered, and the composition and doses are not always clearly reported. A few studies reported no effects, but none reported problems connected to milk thistle administration. However, the overall picture shows that the use of milk thistle results in improved or restored health parameters or better animal performance.

Potomac Horse Fever

Potomac horse fever (PHF) is a common cause of equine colitis in endemic areas. Until recently, the only causative agent known to cause PHF was Neorickettsia risticii. However, N. findlayensis has been isolated from affected horses. Horses typically become infected upon ingestion of Neorickettsia spp.-infected trematodes within aquatic insects. The most common clinical signs include diarrhea, fever, anorexia, lethargy and colic. The diagnostic test of choice for PHF is PCR of blood and feces. Tetracyclines remain an effective treatment. Supportive care, including fluid therapy, colloid administration, NSAID and anti-endotoxin medication, and digital cryotherapy, is also necessary in some cases.

Spontaneous Sepsis in Adult Horses: From Veterinary to Human Medicine Perspectives

Sepsis is a life-threatening disease defined as an organ dysfunction caused by a dysregulated host response to an infection. Early diagnosis and prognosis of sepsis are necessary for specific and timely treatment. However, no predictive biomarkers or therapeutic targets are available yet, mainly due to the lack of a pertinent model. A better understanding of the pathophysiological mechanisms associated with sepsis will allow for earlier and more appropriate management. For this purpose, experimental models of sepsis have been set up to decipher the progression and pathophysiology of human sepsis but also to identify new biomarkers or therapeutic targets. These experimental models, although imperfect, have mostly been performed on a murine model. However, due to the different pathophysiology of the species, the results obtained in these studies are difficult to transpose to humans. This underlines the importance of identifying pertinent situations to improve patient care. As humans, horses have the predisposition to develop sepsis spontaneously and may be a promising model for spontaneous sepsis. This review proposes to give first an overview of the different animal species used to model human sepsis, and, secondly, to focus on adult equine sepsis as a spontaneous model of sepsis and its potential implications for human and veterinary medicine.

Red cell distribution width values and red cell distribution width-to-platelet ratio in Thoroughbred foals in the first 24 hours of life

OBJECTIVES

To report red cell distribution width (RDW) values, to calculate RDW-to-platelet ratio (RPR), and to investigate a possible correlation of RDW and RPR index values in neonatal foals classified as healthy or at risk based on clinical information from a population of foals up to 24 hours of life.

DESIGN

Retrospective study conducted from records and CBCs of foals born between June and November from 2018 to 2020 foaling seasons.

SETTING

Breeding farm.

ANIMALS

Three hundred and nine neonatal full-term Thoroughbred foals.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Foals were evaluated by a veterinarian within 15 minutes after birth, and a blood sample was collected within 24 hours of life. Based on clinical information, 88 of 309 foals (28.4%) were considered at risk of perinatal disease, and 201 were healthy. Mean gestational age for the foals was 346.3 ± 9.7 days. RDW values did not differ between groups. Gestational length demonstrated to have a negative correlation with RDW (r = -0.156, P = 0.005) and mean corpuscular volume (r = -0.135, P = 0.01), indicating a link of these variables to foal maturity. RPR index was higher for at-risk (0.073 ± 0.018) than for healthy foals (0.068 ± 0.014, P = 0.01).

CONCLUSION

RPR might be a promising early indicator of disease for the field triage of neonatal foals.

TLR4 and MD2 variation among horses with differential TNFα baseline concentrations and response to intravenous lipopolysaccharide infusion

Gram-negative bacterial septicemia is mediated through binding of lipopolysaccharide (LPS) to mammalian toll-like receptor protein 4 (TLR4). TLR4 and its cognate protein, myeloid differentiation factor 2 (MD2) form a heterodimeric complex after binding LPS. This complex induces a cascade of reactions that results in increased proinflammatory cytokine gene expression, including TNFα, which leads to activation of innate immunity. In horses, the immune response to LPS varies widely. To determine if this variation is due to differences in TLR4 or MD2, DNA from 15 healthy adult horses with different TNFα dynamics after experimental intravenous LPS infusion was sequenced across exons of TLR4 and MD2. Haplotypes were constructed for both genes using all identified variants. Four haplotypes were observed for each gene. No significant associations were found between either TNFα baseline concentrations or response to LPS and haplotype; however, there was a significant association (P value = 0.0460) between the baseline TNFα concentration and one MD2 missense variant. Three-dimensional structures of the equine TLR4-MD2-LPS complex were built according to haplotype combinations observed in the study horses, and the implications of missense variants on LPS binding were modeled. Although the sample size was small, there was no evidence that variation in TLR4 or MD2 explains the variability in TNFα response observed after LPS exposure in horses.

The fecal bacterial microbiota of healthy and sick newborn foals

BACKGROUND

The fecal bacterial microbiota of normal foals and foals with enterocolitis has been characterized using next-generation sequencing technology; however, there are no reports investigating the gut microbiota in foals hospitalized for other perinatal diseases.

OBJECTIVE

To describe and compare the fecal bacterial microbiota in healthy and sick foals using next-generation sequencing techniques.

ANIMALS

Hospitalized (17) and healthy foals (21).

METHODS

Case-control study. Fecal samples were collected from healthy and sick foals on admission. Sick foals were further divided into sick nonseptic (SNS, n = 9) and septic (n = 8) foals. After extraction of DNA, the V4 region of the 16 S rRNA gene was amplified using a PCR assay, and the final product was sequenced with an Illumina MiSeq.

RESULTS

Diversity was significantly lower in healthy than sick foals (P < .05). The bacterial membership (Jaccard index) and structure (Yue & Clayton index) of the fecal microbiota of healthy, septic, and SNS foals were similar (AMOVA, P > .05). Bacterial membership (AMOVA, P = .06) and structure (AMOVA, P = .33) were not different between healthy and sick foals. Enterobacteriaceae, Enterococcus, and Streptococcus were among the 5 more abundant taxa identified in both groups.

CONCLUSION AND CLINICAL IMPORTANCE

Higher fecal microbiota diversity in sick than healthy foals might suggest a high exposure to environmental microorganisms or an unstable colonic microbiota. The presence of microorganisms causing bacteremia in foals in a high relative abundance in the feces of foals suggests the intestine might play an essential role in the causation of bacteremia in foals.

TLR-activated mesenchymal stromal cell therapy and antibiotics to treat multi-drug resistant Staphylococcal septic arthritis in an equine model

BACKGROUND

Rapid development of antibiotic resistance necessitates advancement of novel therapeutic strategies to treat infection. Mesenchymal stromal cells (MSC) possess antimicrobial and immunomodulatory properties, mediated through antimicrobial peptide secretion and recruitment of innate immune cells including neutrophils and monocytes. TLR-3 activation of human, canine and equine MSC has been shown to enhance bacterial killing and clearance in vitro, in rodent Staphylococcal biofilm infection models and dogs with spontaneous multi-drug-resistant infections. The objective of this study was to determine if intra-articular (IA) TLR-3-activated MSC with antibiotics improved clinical parameters and reduced bacterial counts and inflammatory cytokine concentrations in synovial fluid (SF) of horses with induced septic arthritis.

METHODS

Eight horses were inoculated in one tarsocrural joint with multidrug-resistant Staphylococcus aureus (S. aureus). Bone marrow-derived MSC from three unrelated donors were activated with TLR-3 agonist polyinosinic, polycytidylic acid (pIC). Recipient horses received MSC plus vancomycin (TLR-MSC-VAN), or vancomycin (VAN) alone, on days 1, 4, 7 post-inoculation and systemic gentamicin. Pain scores, quantitative bacterial counts (SF, synovium), SF analyses, complete blood counts, cytokine concentrations (SF, plasma), imaging changes (MRI, ultrasound, radiographs), macroscopic joint scores and histologic changes were assessed. Results were reported as mean ± SEM.

RESULTS

Pain scores (d7, P=0.01, 15.2±0.2 vs. 17.9±0.5), ultrasound (d7, P=0.03, 9.0±0.6 vs. 11.8±0.5), quantitative bacterial counts (SF d7, P=0.02, 0±0 vs. 3.4±0.4; synovium P=0.003, 0.4±0.4 vs. 162.7±18.4), systemic neutrophil (d4, P=0.03, 4.6±0.6 vs. 7.8±0.6) and serum amyloid A (SAA) (d4, P=0.01, 1,106.0±659.0 vs. 2,858.8±141.3; d7, P=0.02, 761.8±746.2 vs. 2,357.3±304.3), and SF lactate (d7, P<0.0001, 5.4±0.2 vs. 15.0±0.3), SAA (endterm, P=0.01, 0.0 vs. 2,094.0±601.6), IL-6 (P=0.03, 313.0±119.2 vs. 1,328.2±208.9), and IL-18 (P=0.02, 11.1±0.5 vs. 13.3±3.8) were improved in TLR-MSC-VAN vs. VAN horses. Study limitations include the small horse sample size, short study duration, and lack of additional control groups.

CONCLUSIONS

Combined TLR-activated MSC with antibiotic therapy may be a promising approach to manage joint infections with drug resistant bacteria.

Serum amyloid A as a marker to detect sepsis and predict outcome in hospitalized neonatal foals

BACKGROUND

Serum amyloid A (SAA) has been reported to hold promise as diagnostic and prognostic marker in foals. This has not been investigated thoroughly.

OBJECTIVES

Evaluate admission SAA concentrations as predictor of sepsis and outcome.

ANIMALS

Five hundred and ninety hospitalized foals <14 days old.

METHODS

Retrospective multicenter study. Foals were scored with sepsis and survival scores, grouped according to health category (septic, sick but nonseptic, uncertain sepsis status) and outcome; septic foals were further categorized according to severity (normal sepsis, severe sepsis, and septic shock). SAA was compared between groups using Mann-Whitney test and Kruskal-Wallis test. Receiver operating characteristic curves identified optimal SAA cut off values for detecting sepsis and predicting outcome.

RESULTS

Admission SAA concentrations differed significantly between sick nonseptic foals (312.1 ± 685.4 mg/L) and septic foals (1079.7 ± 1254.5 mg/L) and increased with increasing sepsis score. SAA did not differ between sepsis severity groups. The optimal cut off for sepsis detection was 1050 mg/L (sensitivity 30.2%, specificity 90.7%). Admission SAA concentrations were lower in surviving (435.0 ± 723.6 mg/L) compared to nonsurviving foals (1062.7 ± 1440.1 mg/L) and decreased with increasing survival score. The optimal cut off for nonsurvival prediction was 1250 mg/L (sensitivity 22.1%, specificity 90.8%).

CONCLUSIONS AND CLINICAL IMPORTANCE

SAA concentration was higher in septic foals and nonsurviving foals. Even though optimal cut offs for SAA to detect sepsis and predict outcome had low sensitivity, they had good specificity. SAA can therefore be used as a marker to rule out sepsis and nonsurvival.

Bacterial pneumonia in horses associated with Escherichia coli infection: report of five cases

ABSTRACT Respiratory diseases have a major impact on sport horses and are often cited as the second most common reason for loss of training days and significant veterinary costs. Adult horses most commonly develop pneumonia when bacteria aspirated from the environment, nose, or oropharynx reach the lower airways and overwhelm the pulmonary defense mechanisms. This article report five cases of bacterial pneumonia in horses associated with infection by Eschericia coli. Five Quarter horses, three males and two females, with ages varying from 5 to 12 years, were examined for diagnosis of respiratory disease characterized by apathy, cough and lack of appetite. Auscultation of the thorax revealed increased harsh breath sounds dorsally, crackles, wheezes, and dullness of respiratory sounds ventrally. Manipulation of the trachea and larynx induced cough. Culture results were positive for Escherichia coli. The therapeutic protocol consisted of anti-inflammatory, antibiotic therapy, and supportive care. Flunixin meglumine was administered intravenously at 24-hour intervals over eight days. Ceftiofur sodium was prescribed intramuscularly, q.d., for 15 days. Horses were clinically monitored daily until complete remission of clinical signs. None of the animals relapsed, and all returned to routine athletic activities.

Risk factors and diseases associated with failure of natural passive immunization in foals

ABSTRACT This study aimed to report the prevalence of diseases in foals, patients at the Hospital Veterinário de Grandes Animais, Universidade Federal de Lavras (HVGA-UFLA), and its association with deaths and possible failures in the transfer of passive immunity (FTIP) via colostrum. Data were obtained from clinical records of horses aged between 0 and 3 months, admitted to the HVGA between January/2014 and December/2018. Descriptive analyzes of the diseases and organ systems affected were performed, as well as univariate analyzes with chi-square or Fisher's exact tests, identifying possible associations between FTIP, infectious diseases and other factors. No significant relationships were found between FTIP and infectious disease, meconium retention, sepsis, or death. However, it was shown that animals weighing between 10 and 30kg were 29.333 times more likely (95% confidence interval 1.734 - 505.951) to die than those weighing between 30.1 and 130kg. Therefore, it can be concluded that low weight is a very relevant risk factor, which may be related to the failure of postural reflexes and, consequently, to the inability to ingest colostrum, impairing the ability to respond to infectious agents.

Biomarkers of sepsis in pigs, horses and cattle: from acute phase proteins to procalcitonin

Sepsis is a complex clinical syndrome triggered by an inflammatory host response to an infection. It is usually complicated to detect and diagnose, and has severe consequences in human and veterinary health, especially when treatment is not started early. Therefore, efforts to detect sepsis accurately are needed. In addition, its proper diagnosis could reduce the misuse of antibiotics, which is essential fighting against antimicrobial resistance. This case is a particular issue in farm animals, as antibiotics have been traditionally given massively, but now they are becoming increasingly restricted. When sepsis is suspected in animals, the most frequently used biomarkers are acute phase proteins such as C-reactive protein, serum amyloid A and haptoglobin, but their concentrations can increase in other inflammatory conditions. In human patients, the most promising biomarkers to detect sepsis are currently procalcitonin and presepsin, and there is a wide range of other biomarkers under study. However, there is little information on the application of these biomarkers in veterinary species. This review aims to describe the general concepts of sepsis and the current knowledge about the biomarkers of sepsis in pigs, horses, and cattle and to discuss possible advances in the field.

A Proteomic Approach to Elucidate the Changes in Saliva and Serum Proteins of Pigs with Septic and Non-Septic Inflammation

Sepsis is a systemic inflammatory response triggered by an infectious agent and is recognized by the World Health Organization as a global concern, since it is one of the major causes of severe illness in humans and animals. The study of the changes that can occur in saliva and serum in sepsis can contribute to a better understanding of the pathophysiological mechanisms involved in the process and also to discover potential biomarkers that can help in its diagnosis and monitoring. The objective of this study was to characterize the changes that occur in the salivary and serum proteome of pigs with experimentally-induced sepsis. The study included five pigs with sepsis induced by LPS administration and five pigs with non-septic inflammation induced by turpentine for comparative purposes. In saliva, there were eighteen salivary proteins differentially expressed in the sepsis condition and nine in non-septic inflammation. Among these, significant increments in aldolase A and serpin B12 only occurred in the sepsis model. Changes in aldolase A were validated in a larger population of pigs with sepsis due to Streptococcus suis infection. In serum, there were 30 proteins differentially expressed in sepsis group and 26 proteins in the non-septic group, and most of the proteins that changed in both groups were related to non-specific inflammation. In the saliva of the septic animals there were some specific pathways activated, such as the organonitrogen compound metabolic process and lipid transport, whereas, in the serum, one of the main activated pathways was the regulation of protein secretion. Overall, saliva and serum showed different proteome variations in response to septic inflammation and could provide complementary information about the pathophysiological mechanisms occurring in this condition. Additionally, salivary aldolase A could be a potential biomarker of sepsis in pigs that should be confirmed in a larger population.

Viral infection and allergy - What equine immune responses can tell us about disease severity and protection

Horses have many naturally occurring diseases that mimic similar conditions in humans. The ability to conduct environmentally controlled experiments and induced disease studies in a genetically diverse host makes the horse a valuable intermediate model between mouse studies and human clinical trials. This review highlights important similarities in the immune landscape between horses and humans using current research on two equine diseases as examples. First, equine herpesvirus type 1 (EHV-1) infection initiates a series of innate inflammatory signals at its mucosal entry site in the upper respiratory tract. These inflammatory markers are highly synchronized and predictable between individuals during viral respiratory infection and ultimately lead to adaptive immune induction and protection. The timing of early inflammatory signals, followed by specific adaptive immune markers correlating with immunity and protection, allow accurate outbreak tracking and also provide a foundation for understanding the importance of local mucosal immunity during other viral respiratory infections. Second, rare peripheral blood immune cells that promote allergic inflammation can be analyzed during Culicoides hypersensitivity, a naturally occurring type I IgE-mediated allergic disease of horses. Rare immune cells, such as IgE-binding monocytes or basophils, can be studied repeatedly in the horse model to unravel their larger mechanistic role in inflammation during allergic and other inflammatory diseases. We conclude with a survey of all other common equine inflammatory conditions. Together, this review serves as a reference and rationale for the horse as a non-rodent model for immunological research.

Evaluation of Different Methods to Estimate the Transfer of Immunity in Donkey Foals Fed with Colostrum of Good IgG Quality: A Preliminary Study

Simple Summary

Little is known about the passive transfer of immunity in donkey foals and about the different types of analysis that can be performed to assess it. The aims of the present study were to evaluate the correlation between IgG Serum Radial Immunodiffusion, Electrophoresis Gamma Globulins, Electrophoresis Total Protein and the Serum Total Protein analyzed by Refractometry and by Dry Chemistry Analyzer (Biuret) and to estimate serum IgG concentrations using Serum TP. IgG Serum Radial Immunodiffusion showed a good correlation with Electrophoresis Gamma Globulins and a high correlation with Total Protein Electrophoresis, Biuret and Refractometry. All the tests performed may be a useful to estimate the serum IgG in donkey foals’ blood in the first day of life using a specific equation.

Abstract

The aims of the present study were to evaluate the correlation between IgG Serum Radial Immunodiffusion (SRID), Electrophoresis Gamma Globulins (EGG), Electrophoresis Total Protein (ETP) and the serum total protein (TP) analyzed by refractometry and by a dry chemistry analyzer (Biuret) and to estimate serum IgG concentrations using serum TP. A total of 36 samples collected at four different times (birth, 6, 12, 24 h after birth) from nine Amiata donkey foals were evaluated with SRID, EGG, ETP, serum TP Biuret and refractometry. SRID IgG concentration increased significantly over time until T12. Serum TP analyzed with refractometry, electrophoresis and Biuret showed a statistically significant difference between T0 and T6 vs. T12 and T24. A good or strong correlation was found between different tests performed. Equations to quantify serum IgG were created and can be used for estimating the donkey foals’ serum IgG in the first day of life. Serum TP refractometry showed a high correlation with SRID IgG (0.91) which may be a particularly useful and economic instrument to estimate the transfer of immunity in donkey foals during the first day of life. Further studies evaluating a high number of animals are needed in order to set specific cut-off values.

The Effect of Uterine Lavage on Soluble CD14, Chemokine Ligand 2, and Interleukin 10 Levels in Mares With Postpartum Metritis

Postpartum metritis in mares is a life-threatening condition associated with severe clinical signs due to endotoxemia, and it is often followed by complications such as laminitis. Repeated large-volume uterine lavages are commonly recommended as a part of the treatment protocol to remove endotoxin-laden contents from the uterus. It has, however, also been suggested that lavages may increase the uptake of endotoxin into the circulation, leading to a deterioration of clinical signs. Endotoxemia is associated with the release of a multitude of inflammatory mediators regulating the immune response. The aim of this study was to evaluate if uterine lavage influences serum levels of the inflammation markers soluble CD14 (sCD14), chemokine (C-C motif) ligand 2 (CCL2), and interleukin (IL)-10 in mares with postpartum metritis. Serum samples were collected from eight mares treated for metritis at a university teaching hospital. Mares with fever, tachycardia, and/or leukopenia and hemosanguineous or purulent intrauterine fluid within 1 week of foaling were included in the study. Serum samples were taken before uterine lavage and 15 and 30 minutes after starting the lavage. The concentrations of sCD14, CCL2, and IL-10 were determined with a fluorescent bead-based immunoassay. There were no significant differences between sCD14, CCL2, or IL-10 levels at different sampling times. Heart rate was significantly lower after uterine lavage than before. The differences in body temperature and leukocyte count before and after lavage were not significant. In conclusion, uterine lavage had no immediate effect on the serum concentration of sCD14, CCL2, or IL-10, nor did it affect clinical parameters negatively.

Serial measurements of Paraoxonase-1 (PON-1) activity in horses with experimentally induced endotoxemia

Background

Paraoxonase-1 (PON-1) is an antioxidant enzyme, whose activity decreases during the acute phase response in many species. Little is known about PON-1 and its role as a negative acute phase protein during septic inflammation in horses, but promising findings about its utility in diagnosing SIRS and predicting the outcome in diseased horses, were recently highlighted. The objective of the study was to investigate the behaviour of PON-1 in horses after experimentally induced endotoxemia. To this aim, PON-1 activity was measured on 66 plasma samples collected from six clinically healthy mares, previously included in another study, before and at multiple time points between 12 and 240 h after intravenous infusion of Escherichia coli O55:B5 lipopolysaccharide (LPS).

Results

Compared with baseline values, a progressive transient decrease of PON-1 activity was observed starting from 24 h post-infusion, with lowest values observed between 3 to 7 days post-infusion, followed by a normalisation to pre-infusion levels the tenth day.

Conclusions

The results of this study suggest that measurement and monitoring of PON-1 activity might be useful to evaluate progression and recovery from endotoxemia in horses. Further studies in horses with naturally occurring sepsis are warranted.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-020-02629-4.

Protective Effect of Silibinin on Lipopolysaccharide-Induced Inflammatory Responses in Equine Peripheral Blood Mononuclear Cells, an In Vitro Study

Simple Summary

Natural compounds are often an important source of biologically active molecules, which can find important applications in the treatment or pharmacological prevention of several pathologies. Silibinin is a natural polyphenolic flavonoid that is extracted from plant milk thistle, Silybum marianum. Silibinin has been reported to have antioxidant and immunomodulatory and anti-inflammatory activities. In horses, in particular, inflammation secondary to bacterial infection or translocation is one of the most frequent causes of morbidity and mortality. The aim of this study was to test the effect of silibinin on lipopolysaccharide (LPS)-induced inflammatory response in equine peripheral blood mononuclear cells (PBMCs). Taken together, our results showed an interesting prospective in therapeutic use of silibinin in equine inflammatory disease. Furthermore, the results from this study support the evidence of use equine PBMCs as an in vitro model to study inflammatory and immune response and for drug screening into the target specie.

Abstract

Although inflammation is an important physiological response, it plays a prominent role in several diseases across the mammalian species. In horses, in particular, inflammation secondary to bacterial infection or translocation is one of the most frequent causes of morbidity and mortality. Research in new molecules with anti-inflammatory and immunomodulatory proprieties and safe use profile is constantly an active field; natural compounds are an important source of molecules with peculiar properties such as antioxidants, anti-inflammatory and immune modulating. Silibinin, a natural polyphenolic flavonoid, extracted from plant milk thistle, Silybum marianum, has been reported to have actions such as antioxidant immunomodulatory and anti-inflammatory. The aim of this study was to test the effect of silibinin on lipopolysaccharide (LPS)-induced inflammatory response in equine peripheral blood mononuclear cells (PBMCs). Our results showed the protective effect of silibinin 10 μM and 50 μM in equine PBMCs stimulated with LPS. Silibilinin was able to prevent the LPS induced increased levels of TNF-α, IL-1β, IL-6 and IL-8. The results from this study on LPS-stimulated equine PBMCs showed that silibinin could be a useful pharmacological approach in treatment or prevention of several inflammatory conditions in horse.

Factors associated with the risk of positive blood culture in neonatal foals presented to a referral center (2000-2014)

Background

Bloodstream infections (BSI) are common in sick foals and increase foal morbidity and mortality when they occur. Recognition of risk factors for BSI could be an important means to limit their occurrence, but studies on this topic are limited.

Objectives

Historical as well as maternal and foal physical examination findings will predict risk of BSI in neonatal foals.

Animals

Foals <14 days of age admitted to a referral equine hospital for care.

Methods

Retrospective case‐control study with univariate and multivariable logistic regression analysis.

Results

Four hundred twenty‐nine (143 cases and 286 controls) foals <14 days of age were studied. Risk of a foal having a BSI was increased in foals with umbilical disease (adjusted odds ratio [OR], 11.01; P = .02), hypoglycemia (adjusted OR, 13.51; P = .03), and the combined presence of umbilical disease and low hematocrit (adjusted OR, >999.99; P = .04). Factors not found to be risk factors for development of BSI included prematurity, hypothermia, abdominal disease, diarrhea, failure of passive transfer, and maternal uterine infection.

Conclusions and Clinical Importance

Several historical and physical examination findings increase the risk of foals being blood culture positive at presentation to the hospital. This knowledge may aid early identification of blood culture status, thus aiding in treatment decisions.

The composition of the perinatal intestinal microbiota in horse

The establishment of the intestinal microbiota is critical for the digestive and immune systems. We studied the early development of the rectal microbiota in horse, a hindgut fermenter, from birth until 7 days of age, by qPCR and 16S rRNA gene amplicon sequencing. To evaluate initial sources of the foal microbiota, we characterised dam fecal, vaginal and oral microbiotas. We utilised an amplicon sequence variant (ASV) pipeline to maximise resolution and reproducibility. Stringent ASV filtering based on prevalence and abundance in samples and controls purged contaminants while preserving intestinal taxa. Sampled within 20 minutes after birth, rectal meconium contained small amounts of diverse bacterial DNA, with a profile closer to mare feces than mouth. 24 hours after birth, rectum was colonised by Firmicutes and Proteobacteria, some foals dominated by single genera. At day 7, the rectal genera were still different from adult feces. The mare vaginal microbiota contributed to 24 h and 7 day microbiotas. It contained few lactobacilli, with Corynebacterium, Porphyromonas, Campylobacter and Helcococcus as the most abundant genera. In the oral mucosa, Gemella was extremely abundant. Our observations indicate that bacteria or bacterial components are present in the intestine immediately after birth, but the newborn microbiota changes rapidly.

Cytological Findings in Bronchoalveolar Lavage Fluid of Foals With Pneumonia Caused by Rhodococcus equi and Other Bacteria

The distinction between lower respiratory tract infections caused by Rhodococcus equi and those caused by other pathogens is difficult. The aim of this retrospective study was to describe cytological findings in bronchoalveolar lavage fluid (BALF) of foals with pneumonia caused by R. equi or other bacteria. Nineteen foals aged from 3 weeks to 6 months with evidence of respiratory disease between 2015 and 2016 were selected from the database of the Veterinary Teaching Hospital "Mario Modenato" of the University of Pisa. Eight foals of 19 (42.1%) had R. equi pneumonia, whereas 11 of 19 (57.9%) had another bacterial pneumonia. R. equi-positive foals had statistically significant higher total nucleated cell count (P = .02) and neutrophils percentage (P = .002) than R. equi-negative ones. Macrophages proportion (P = .01) was lower in R. equi-positive than in R. equi-negative foals. Bronchoalveolar lavage is a quite easy procedure that can be performed in the field with minimal equipment required. Here we reported significant differences in the cellular composition of BALF that can be used to differentiate foals with R. equi bronchopneumonia from those with other bacterial pneumonias, whereas waiting for culture results.

Endotoxin-induced changes of type VII collagen- cleaving matrix metalloproteinases in lamellar tissue of extracorporeally perfused equine limbs

OBJECTIVE To investigate the effect of lipopolysaccharide (LPS) on type VII collagen- cleaving matrix metalloproteinases (MMPs) in the lamellar tissue of extracorporeally perfused equine limbs. SAMPLE 10 right forelimbs and 3 left forelimbs collected from 10 adult horses after slaughter at a licensed abattoir. PROCEDURES Extracorporeal perfusion of the isolated equine limbs was performed for 10 hours under physiologic conditions (control-perfused limbs; n = 5) and with the addition of 80 ng of LPS/L of perfusate (LPS-perfused limbs; 5). Lamellar tissue specimens were then collected from the dorsal aspect of the hooves. Additionally, corresponding control specimens were collected from the 3 nonperfused left forelimbs. Immunohistochemical analysis was performed on paraffin-embedded tissue blocks with antibodies against total (latent and active) MMP-1, MMP-2, MMP-8, and MMP-9 as well as antibody against active MMP-9. Intensity of immunohistochemical staining was scored, and stain distribution in the lamellar tissue was noted. RESULTS Staining intensity of total and active MMP-9 was significantly increased in LPS-perfused versus control-perfused limbs. No such difference was identified for MMP-1, MMP-2, and MMP-8. CONCLUSIONS AND CLINICAL RELEVANCE Of the 4 MMPs that are capable of degrading type VII collagen, MMP-9 was the only one for which production increased in the lamellar tissue of isolated equine limbs perfused with versus without a clinically relevant concentration of LPS. These results suggested that MMP-9 may be involved in initiation of pathological changes in lamellar tissue in endotoxin-induced laminitis, whereas MMP-1, MMP-2, and MMP-8 may be less relevant.

Comparison of two blood sampling techniques for the determination of coagulation parameters in the horse: Jugular venipuncture and indwelling intravenous catheter

BACKGROUND

Evaluation of coagulation status is an important component of critical care. Ongoing monitoring of coagulation status in hospitalised horses has previously been via serial venipuncture due to concerns that sampling directly from the intravenous catheter (IVC) may alter the accuracy of the results. Adverse effects such as patient anxiety and trauma to the sampled vessel could be avoided by the use of an indwelling IVC for repeat blood sampling.

OBJECTIVES

To compare coagulation parameters from blood obtained by jugular venipuncture with IVC sampling in critically ill horses.

STUDY DESIGN

Prospective observational study.

METHODS

A single set of paired blood samples were obtained from horses (n = 55) admitted to an intensive care unit by direct jugular venipuncture and, following removal of a presample, via an indwelling IVC. The following coagulation parameters were measured on venipuncture and IVC samples: whole blood prothrombin time (PT), fresh plasma PT and activated partial thromboplastin time (aPTT) and stored plasma antithrombin activity (AT) and fibrinogen concentration. D-dimer concentration was also measured in some horses (n = 22). Comparison of venipuncture and IVC results was performed using Lin's concordance correlation coefficient. Agreement between paired results was assessed using Bland Altman analysis.

RESULTS

Correlation was substantial and agreement was good between sample methods for all parameters except AT and D-dimers.

MAIN LIMITATIONS

Each coagulation parameter was tested using only one assay. Sampling was limited to a convenience sample and timing of sample collection was not standardised in relation to when the catheter was flushed with heparinised saline.

CONCLUSIONS

With the exception of AT and D-dimers, coagulation parameters measured on blood samples obtained via an IVC have clinically equivalent values to those obtained by jugular venipuncture.

Factors Associated with Survival in 97 Horses with Septic Pleuropneumonia

BACKGROUND

Septic pleuropneumonia is a common cause of morbidity and mortality in horses, but there is limited data available regarding factors associated with survival.

HYPOTHESIS/OBJECTIVES

To identify factors predictive of survival in horses with septic pleuropneumonia.

ANIMALS

A total of 97 horses with septic pleuropneumonia at 2 referral institutions.

METHODS

A retrospective study was performed. A diagnosis of septic pleuropneumonia was based on the presence of sepsis, pleural effusion, and positive bacterial culture from tracheal aspiration (TA) or pleural fluid (PF).

RESULTS

Thirty-one percent of horses had a recent history of travel. Clinical signs included lethargy (78%), tachycardia (75%), tachypnea (60%), fever (43%), prolonged capillary refill time (22%), and ventral edema (14%). The most common clinicopathologic abnormality was hyperfibrinogenemia (79%). Increased serum creatinine concentration at presentation was negatively associated with survival (OR, 5.13; CI, 1.88-14.01; P = .001) and return to work (OR, 6.46; CI, 1.10-37.92; P = .034). Eighty-four TA and 67 PF samples were submitted for culture, 98 and 84% of which were positive, respectively. The most common isolate was Streptococcus equi subsp zooepidemicus. Tracheal aspirates were more sensitive than PF for bacterial growth, but some organisms isolated from PF were not isolated from TA. Thoracotomy was positively associated with survival (OR, 0.13; CI, 0.01-0.83; P = .028).

CONCLUSIONS AND CLINICAL IMPORTANCE

Increased serum creatinine concentration is a negative prognostic indicator and is likely a reflection of dehydration. Submission of TA and PF is recommended. Thoracotomy should be considered as a treatment for pleuropneumonia.

Expression of von Willebrand factor, pulmonary intravascular macrophages, and Toll-like receptors in lungs of septic foals

Sepsis causes significant mortality in neonatal foals; however, there is little data describing the cellular and molecular pathways of lung inflammation in septic foals. This study was conducted to characterize lung inflammation in septic foals. Lung tissue sections from control (n = 6) and septic (n = 17) foals were compared using histology and immunohistology. Blinded pathologic scoring of hematoxylin and eosin stained samples revealed increased features of lung inflammation such as thickened alveolar septa and sequestered inflammatory cells in septic foals. Septic foal lungs showed increased expression of von Willebrand factor in blood vessels, demonstrating vascular inflammation. Use of MAC387 antibody to detect calprotectin as a reflection of mononuclear cell infiltration revealed a significant increase in their numbers in alveolar septa of lungs from septic foals compared to those from control foals. The mononuclear cells appeared to be mature macrophages and were located in the septal capillaries, suggesting they were pulmonary intravascular macrophages (PIMs). Finally, lungs from septic foals showed increased expression of Toll-like receptor 4 and 9 in mononuclear cells relative to the control. Taken together, this study is the first to show the expression of inflammatory molecules and an increase in PIMs in lungs from foals that died from sepsis.

Kinetics of plasma procalcitonin, soluble CD14, CCL2 and IL-10 after a sublethal infusion of lipopolysaccharide in horses

Endotoxemia represents a significant clinical and economic problem for the equine industry. This study assesses the kinetics of soluble CD14 (sCD14), chemokine (CC motif) ligand 2 (CCL2), interleukin 10 (IL-10) and plasma procalcitonin (PCT) in healthy horses after the intravenous infusion of lipopolysaccharide (LPS). The aim was to contribute to the basic understanding of the equine species-specific kinetics of these molecules in response to LPS exposure, which could support further findings in clinical studies and identify valuable inflammatory biomarkers for equine practice. Eleven healthy horses were involved in this experimental in vivo study. Horses were classified as healthy before the LPS infusion. After the pre-infusion blood collection (T0), all horses received an infusion of E. coli endotoxin (30ng/kg over 30min). Data and samples were collected 1h (T1), 2 (T2), 3 (T3) and 24h (T24) after infusion. Plasma sCD14, CCL2 and IL-10 were evaluated with a fluorescent bead-based assay, while PCT was evaluated with an equine PCT ELISA assay. A one-way ANOVA test was performed between each blood-sampling time for PCT, sCD14 and IL-10, and a Friedman test was performed for CCL2. Plasma PCT, IL-10 and CCL2 concentrations increased statistically significantly at T1, T2 and T3 compared to T0. No statistically significant differences were found between plasma IL-10 and CCL2 concentrations between T0 vs T24, although plasma PCT values remained high 24h after LPS infusion. Plasma sCD14 concentration showed no statistically significant differences for any of sampling times. Our results demonstrate that LPS injection into healthy horses results in PCT, CCL2 and IL-10 increases in plasma without an increase in sCD14. The increases in PCT, CCL2 and IL-10 are related to the inflammatory response induced by circulating lipopolysaccharide.